1. Field of the Invention
This invention relates to a method and apparatus for the connection of a rotary drum drive, particularly a drive of a rotary furnace, after disconnection of the same for a short time and before the oscillating drum reaches a standstill condition.
2. Description of the Prior Art
It is well known in the art that rotary drum and rotary furnace drives are primarily constructed as thyristor controlled direct current drives. Through the inclined position of the drum or combustion material carried thereby and upon addition of material on one side of the drum, the rotating drum swings, or in a rotary furnace the rotary furnace pipe swings, as a pendulum in an oscillatory manner for several minutes about a point of equilibrium after disconnection of the drive. In order to prevent, upon reconnection of the drive, a swing of the rotary drum or rotary furnace in a direction opposite to that of the drive direction, it has heretofore been the practice in rotary furnace drives to provide a time delay of about 5 to 10 minutes before a new connection was possible. It was thereby ensured that the rotary furnace had come to a standstill before reconnection. This great safety time interval, however, particularly in connection with large rotary furnace installations, was found to be very disturbing, as the reconnection in the normal course of operation could have taken place more rapidly and often in much shorter time after the disconnection, but for the requirement that the oscillating part reach a standstill condition. Particularly upon introduction or upon taking into operation, respectively, of a new rotary drum or a rotary furnace installation, or upon inspections of such equipment, the drive must be disconnected more frequently, so that the unproductive standstill periods and waiting periods accumulate and therefore lead to an overall less efficient operation.